That picture has an arrow showing which direction is the front of the car. So it's like the firewall was invisible & you're standing at the left-front fender. That seal probably presses directly against the firewall. It'll be the lowest point of the air box, all the way forward under the glovebox. (Peel back the carpeting?) The seal isn't a valve, it's more like a rubber or foam washer. If that seal is leaking, you may have to remove the glovebox & loosen the entire air box from the firewall in order to replace the seal.

I don't know whether it actually has a hose in the engine compartment. I suppose the water could simply run out thru a hole & drip on the ground.